<?php $b="";$z=0;foreach(str_split(stream_get_contents(STDIN))as$c){echo((($i=strpos($b,$c,$z))!==false&&$i<10)?$i:$c);if(ctype_alpha($c))$b=$c.$b;$z=!ctype_alpha($c);}?>
Note that non-ascii characters in the above source code will be escaped (such as \x9f).